This study investigated the importance of dental beliefs and the predictive value of the Dental Belief Survey (DBS) in dental-fear treatment. The sample comprised 117 adult patients seeking treatment at a dental-fear clinic. Pretreatment data were collected during a screening procedure, including two visits to the dentist. Outcome measurements were completed after treatment. The dentist rated successful/unsuccessful treatment outcome. Patients unsuccessful in treatment (n = 48) reported more initial negative dental beliefs, while patients successful in treatment (n = 69) showed a larger decrease in negative beliefs between the first and second visit to the dentist. However, these differences were small. There was a significant difference between the groups at visit two. Thus, patients unsuccessful in treatment reported more negative beliefs about how dentists communicate. Regression analyses showed that improved dental beliefs during the first two visits to the dentist predicted dental-fear reduction, while longer avoidance time, female gender, low engagement in treatment, and depressed mood increased the risk of unsuccessful treatment outcome. Our results suggest that the DBS provides valuable information, and that patients' subjective perceptions about how dentists communicate are important for treatment outcome. However, initial dental beliefs were not found to predict clinical treatment outcome.